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    <title>clSetEventCallback</title>
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    <div class="refentry">
      <a id="id-1"></a>
      <div class="titlepage"></div>
      <div xmlns="" class="refnamediv">
        <a xmlns="http://www.w3.org/1999/xhtml" id="clSetEventCallback"></a>
        <h1>
            clSetEventCallback
        </h1>
        <p>
            Registers a user callback function for a specific command execution status.
        </p>
      </div>
      <div class="refsynopsisdiv">
        <h2></h2>
        <div class="funcsynopsis">
          <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
            <tr valign="bottom">
              <td>
                <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef">
                    <a class="link" href="scalarDataTypes.html" target="pagedisplay">cl_int</a> <strong class="fsfunc">clSetEventCallback</strong>
                (</code>
                <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="abstractDataTypes.html" target="pagedisplay">cl_event</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">event</var>, </td>
              </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td>
                    <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="pagedisplay">cl_int</a>
                     <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">command_exec_callback_type</var>
                , </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="pagedisplay">void</a> (CL_CALLBACK  <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*pfn_event_notify)
                (<a class="link" href="abstractDataTypes.html" target="pagedisplay">cl_event</a> event, <a class="link" href="scalarDataTypes.html" target="_top">cl_int</a> event_command_exec_status,
                 <a class="link" href="scalarDataTypes.html" target="pagedisplay">void</a> *user_data</var>), </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="pagedisplay">void</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*user_data</var><code>)</code></td>
            </tr>
          </table>
        </div>
      </div>
      <div class="refsect1">
        <a id="parameters"></a>
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">
                <code class="varname">event</code>
              </span>
            </dt>
            <dd>
              <p>A valid event object.</p>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">command_exec_callback_type</code>
              </span>
            </dt>
            <dd>
              <p>
                       The command execution status for which
                      the callback is registered. The command execution callback value for
                      which a callback can be registered is <code class="constant">CL_SUBMITTED</code>,
                      <code class="constant">CL_RUNNING</code>, or <code class="constant">CL_COMPLETE</code>.
                      There is no guarantee that the callback functions registered for various
                      execution status values for an event will be called in the exact order
                      that the execution status of a command changes. Furthermore, it should
                      be noted that receiving a call back for an event with a status other than
                      <code class="constant">CL_COMPLETE</code>, in no way implies that the memory model
                      or execution model as defined by the OpenCL specification has changed. For
                      example, it is not valid to assume that a corresponding memory transfer has
                      completed unless the event is in a state <code class="constant">CL_COMPLETE</code>.
                    </p>
              <p>
                      The callback function registered for a
                      <code class="varname">command_exec_callback_type</code> value of
                      <code class="constant">CL_COMPLETE</code> will be called when the command has
                      completed successfully or is abnormally terminated.
                    </p>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">pfn_event_notify</code>
              </span>
            </dt>
            <dd>
              <p>
                       The event callback function that can be
                      registered by the application. This callback function may be called
                      asynchronously by the OpenCL implementation. It is the application's
                      responsibility to ensure that the callback function is thread-safe. The
                      parameters to this callback function are:
                    </p>
              <div class="itemizedlist">
                <ul class="itemizedlist" style="list-style-type: disc; ">
                  <li class="listitem" style="list-style-type: disc"><code class="varname">event</code> is the event object for which the callback function is invoked.
                        </li>
                  <li class="listitem" style="list-style-type: disc"><code class="varname">event_command_exec_status</code> represents the
                          execution status of command for which this callback function is
                          invoked. See the table of values for <code class="varname">param_value</code> for
                          <a class="citerefentry" href="clGetEventInfo.html"><span class="citerefentry"><span class="refentrytitle">clGetEventInfo</span></span></a>
                          for the command execution status values. If the callback is called as the
                          result of the command associated with event being abnormally terminated,
                          an appropriate error code for the error that caused the termination
                          will be passed to <code class="varname">event_command_exec_status</code> instead.
                        </li>
                  <li class="listitem" style="list-style-type: disc"><code class="varname">user_data</code> is a pointer to user supplied data.
                        </li>
                </ul>
              </div>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">user_data</code>
              </span>
            </dt>
            <dd>
              <p>
                       Will be passed as the
                      <code class="varname">user_data</code> argument when <code class="varname">pfn_notify</code>
                      is called. <code class="varname">user_data</code> can be NULL.
                    </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1">
        <a id="notes"></a>
        <h2>Notes</h2>
        <p>
          The registered callback function will be called when the execution status of command
          associated with <code class="varname">event</code> changes to an execution status equal to or
          past the status specified by <code class="varname">command_exec_status</code>.
        </p>
        <p>
          Each call to <code class="function">clSetEventCallback</code> registers the specified user
          callback function on a callback stack associated with <code class="varname">event</code>. The
          order in which the registered user callback functions are called is undefined.
        </p>
        <p>
          All callbacks registered for an event object must be called. All enqueued callbacks shall
          be called before the event object is destroyed. Callbacks must return promptly. The
          behavior of calling expensive system routines, OpenCL API calls to create contexts
          or command-queues, or blocking OpenCL operations from the following list below,
          in a callback is undefined.
        </p>
        <div class="itemizedlist">
          <ul class="itemizedlist" style="list-style-type: disc; ">
            <li class="listitem" style="list-style-type: disc">
              <a class="citerefentry" href="clFinish.html">
                <span class="citerefentry">
                  <span class="refentrytitle">clFinish</span>
                </span>
              </a>
            </li>
            <li class="listitem" style="list-style-type: disc">
              <a class="citerefentry" href="clWaitForEvents.html">
                <span class="citerefentry">
                  <span class="refentrytitle">clWaitForEvents</span>
                </span>
              </a>
            </li>
            <li class="listitem" style="list-style-type: disc">
              blocking calls to
              <a class="citerefentry" href="clEnqueueReadBuffer.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueReadBuffer</span></span></a>,
              <a class="citerefentry" href="clEnqueueReadBufferRect.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueReadBufferRect</span></span></a>,
              <a class="citerefentry" href="clEnqueueWriteBuffer.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueWriteBuffer</span></span></a>, and
              <a class="citerefentry" href="clEnqueueWriteBufferRect.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueWriteBufferRect</span></span></a></li>
            <li class="listitem" style="list-style-type: disc">
              blocking calls to
              <a class="citerefentry" href="clEnqueueReadImage.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueReadImage</span></span></a>
              and <a class="citerefentry" href="clEnqueueWriteImage.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueWriteImage</span></span></a></li>
            <li class="listitem" style="list-style-type: disc">
              blocking calls to
              <a class="citerefentry" href="clEnqueueMapBuffer.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueMapBuffer</span></span></a>
              and <a class="citerefentry" href="clEnqueueMapImage.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueMapImage</span></span></a></li>
            <li class="listitem" style="list-style-type: disc">
              blocking calls to
              <a class="citerefentry" href="clBuildProgram.html"><span class="citerefentry"><span class="refentrytitle">clBuildProgram</span></span></a>,
              <a class="citerefentry" href="clCompileProgram.html"><span class="citerefentry"><span class="refentrytitle">clCompileProgram</span></span></a>,
              or <a class="citerefentry" href="clLinkProgram.html"><span class="citerefentry"><span class="refentrytitle">clLinkProgram</span></span></a>.
            </li>
          </ul>
        </div>
        <p>
          If an application needs to wait for completion of a routine from the above list in a
          callback, please use the non-blocking form of the function, and assign a completion
          callback to it to do the remainder of your work. Note that when a callback (or other
          code) enqueues commands to a command-queue, the commands are not required to begin
          execution until the queue is flushed. In standard usage, blocking enqueue calls serve
          this role by implicitly flushing the queue. Since blocking calls are not permitted in
          callbacks, those callbacks that enqueue commands on a command queue should either
          call <a class="citerefentry" href="clFlush.html"><span class="citerefentry"><span class="refentrytitle">clFlush</span></span></a>
          on the queue before returning or arrange for
          <a class="citerefentry" href="clFlush.html"><span class="citerefentry"><span class="refentrytitle">clFlush</span></span></a> to be called
          later on another thread.
        </p>
      </div>
      <div class="refsect1">
        <a id="errors"></a>
        <h2>Errors</h2>
        <p>
          Returns <span class="errorname">CL_SUCCESS</span> if the function is executed
          successfully. Otherwise, it returns one of the following errors:
        </p>
        <div class="itemizedlist">
          <ul class="itemizedlist" style="list-style-type: disc; ">
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_EVENT</span> if <code class="varname">event</code> is not a valid event object.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_VALUE</span> if <code class="varname">pfn_event_notify</code> is NULL or if
                <code class="varname">command_exec_callback_type</code> is not <code class="constant">CL_COMPLETE</code>.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_OUT_OF_RESOURCES</span> if there is a failure to allocate resources required
                by the OpenCL implementation on the device.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_OUT_OF_HOST_MEMORY</span> if there is a failure to allocate resources
                required by the OpenCL implementation on the host.
            </li>
          </ul>
        </div>
      </div>
      <div class="refsect1">
        <a id="specification"></a>
        <h2>Specification</h2>
        <p>
            <img src="pdficon_small1.gif" />

            <a href="http://www.khronos.org/registry/cl/specs/opencl-1.2.pdf#page=183" target="OpenCL Spec">OpenCL Specification</a>
        </p>
      </div>
      <div xmlns="" class="refsect3" lang="en" xml:lang="en"><a xmlns="http://www.w3.org/1999/xhtml" id="Copyright"></a><h4 xmlns="http://www.w3.org/1999/xhtml"></h4><img xmlns="http://www.w3.org/1999/xhtml" src="KhronosLogo.jpg" /><p xmlns="http://www.w3.org/1999/xhtml"></p>Copyright © 2007-2011 The Khronos Group Inc.
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and/or associated documentation files (the
"Materials"), to deal in the Materials without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Materials, and to
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the condition that this copyright notice and permission notice shall be included
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